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42 <H1 class="no-header">curs_color 3x 2024-04-20 ncurses 6.5 Library calls</H1>
44 <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG> Library calls <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>
49 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
50 <STRONG>start_color</STRONG>, <STRONG>has_colors</STRONG>, <STRONG>can_change_color</STRONG>, <STRONG>init_pair</STRONG>, <STRONG>init_color</STRONG>,
51 <STRONG>init_extended_pair</STRONG>, <STRONG>init_extended_color</STRONG>, <STRONG>color_content</STRONG>, <STRONG>pair_content</STRONG>,
52 <STRONG>extended_color_content</STRONG>, <STRONG>extended_pair_content</STRONG>, <STRONG>reset_color_pairs</STRONG>,
53 <STRONG>COLOR_PAIR</STRONG>, <STRONG>PAIR_NUMBER</STRONG>, <STRONG>COLORS</STRONG>, <STRONG>COLOR_PAIRS</STRONG>, <STRONG>COLOR_BLACK</STRONG>, <STRONG>COLOR_RED</STRONG>,
54 <STRONG>COLOR_GREEN</STRONG>, <STRONG>COLOR_YELLOW</STRONG>, <STRONG>COLOR_BLUE</STRONG>, <STRONG>COLOR_MAGENTA</STRONG>, <STRONG>COLOR_CYAN</STRONG>,
55 <STRONG>COLOR_WHITE</STRONG> - manipulate terminal colors with <EM>curses</EM>
58 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
59 <STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
61 <EM>/*</EM> <EM>variables</EM> <EM>*/</EM>
62 <STRONG>int</STRONG> <STRONG>COLOR_PAIRS;</STRONG>
63 <STRONG>int</STRONG> <STRONG>COLORS;</STRONG>
65 <STRONG>int</STRONG> <STRONG>start_color(void);</STRONG>
67 <STRONG>bool</STRONG> <STRONG>has_colors(void);</STRONG>
68 <STRONG>bool</STRONG> <STRONG>can_change_color(void);</STRONG>
70 <STRONG>int</STRONG> <STRONG>init_pair(short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>f</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>b</EM><STRONG>);</STRONG>
71 <STRONG>int</STRONG> <STRONG>init_color(short</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>r</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>g</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>b</EM><STRONG>);</STRONG>
72 <EM>/*</EM> <EM>extensions</EM> <EM>*/</EM>
73 <STRONG>int</STRONG> <STRONG>init_extended_pair(int</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>f</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>b</EM><STRONG>);</STRONG>
74 <STRONG>int</STRONG> <STRONG>init_extended_color(int</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>r</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>g</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>b</EM><STRONG>);</STRONG>
76 <STRONG>int</STRONG> <STRONG>color_content(short</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>r</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>g</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
77 <STRONG>int</STRONG> <STRONG>pair_content(short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>f</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
78 <EM>/*</EM> <EM>extensions</EM> <EM>*/</EM>
79 <STRONG>int</STRONG> <STRONG>extended_color_content(int</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>r</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>g</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
80 <STRONG>int</STRONG> <STRONG>extended_pair_content(int</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>f</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
82 <EM>/*</EM> <EM>extension</EM> <EM>*/</EM>
83 <STRONG>void</STRONG> <STRONG>reset_color_pairs(void);</STRONG>
85 <STRONG>int</STRONG> <STRONG>COLOR_PAIR(int</STRONG> <EM>n</EM><STRONG>);</STRONG>
86 <STRONG>PAIR_NUMBER(int</STRONG> <EM>attr</EM><STRONG>);</STRONG>
89 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
91 </PRE><H3><a name="h3-Overview">Overview</a></H3><PRE>
92 <EM>curses</EM> supports color attributes on terminals with that capability.
93 Call <STRONG>start_color</STRONG> (typically right after <STRONG><A HREF="curs_initscr.3x.html">initscr(3x)</A></STRONG>) to enable this
94 feature. Colors are always used in pairs. A <EM>color</EM> <EM>pair</EM> couples a
95 foreground color for characters with a background color for the blank
96 field on which characters are rendered. <STRONG>init_pair</STRONG> initializes a color
97 pair. The macro <STRONG>COLOR_PAIR</STRONG>(<EM>n</EM>) can then convert the pair to a video
100 If a terminal has the relevant capability, <STRONG>init_color</STRONG> permits
101 (re)definition of a color. <STRONG>has_colors</STRONG> and <STRONG>can_change_color</STRONG> return <STRONG>TRUE</STRONG>
102 or <STRONG>FALSE</STRONG>, depending on whether the terminal has color capability and
103 whether the programmer can change the colors. <STRONG>color_content</STRONG> permits
104 extraction of the red, green, and blue components of an initialized
105 color. <STRONG>pair_content</STRONG> permits discovery of a color pair's current
109 </PRE><H3><a name="h3-Rendering">Rendering</a></H3><PRE>
110 <EM>curses</EM> combines the following data to render a character cell. Any of
111 them can include color information.
113 <STRONG>o</STRONG> <EM>curses</EM> character attributes, as from <STRONG><A HREF="curs_addch.3x.html">waddch(3x)</A></STRONG> or <STRONG><A HREF="curs_add_wch.3x.html">wadd_wch(3x)</A></STRONG>
115 <STRONG>o</STRONG> window attributes, as from <STRONG><A HREF="curs_attr.3x.html">wattrset(3x)</A></STRONG> or <STRONG><A HREF="curs_attr.3x.html">wattr_set(3x)</A></STRONG>
117 <STRONG>o</STRONG> window background character attributes, as from <STRONG><A HREF="curs_bkgd.3x.html">wbkgdset(3x)</A></STRONG> or
118 <STRONG><A HREF="curs_bkgrnd.3x.html">wbkgrndset(3x)</A></STRONG>
120 Per-character and window attributes are usually set through a function
121 parameter containing attributes including a color pair value. Some
122 functions, such as <STRONG>wattr_set</STRONG>, use a separate color pair number
125 The background character is a special case: it includes a character
126 code, just as if it were passed to <STRONG>waddch</STRONG>.
128 The <EM>curses</EM> library does the actual work of combining these color pairs
129 in an internal function called from <STRONG>waddch</STRONG>:
131 <STRONG>o</STRONG> If the parameter passed to <STRONG>waddch</STRONG> is <EM>blank</EM>, and it uses the special
134 <STRONG>o</STRONG> <EM>curses</EM> next checks the window attribute.
136 <STRONG>o</STRONG> If the window attribute does not use color pair 0, <EM>curses</EM> uses
137 the color pair from the window attribute.
139 <STRONG>o</STRONG> Otherwise, <EM>curses</EM> uses the background character.
141 <STRONG>o</STRONG> If the parameter passed to <STRONG>waddch</STRONG> is <EM>not</EM> <EM>blank</EM>, or it does not use
142 the special color pair 0, <EM>curses</EM> prefers the color pair from the
143 parameter, if it is nonzero. Otherwise, it tries the window
144 attribute next, and finally the background character.
146 Some <EM>curses</EM> functions such as <STRONG>wprintw</STRONG> call <STRONG>waddch</STRONG>. Those do not
147 combine its parameter with a color pair. Consequently those calls use
148 only the window attribute or the background character.
151 </PRE><H2><a name="h2-CONSTANTS">CONSTANTS</a></H2><PRE>
152 In <STRONG><curses.h></STRONG> the following macros are defined. These are the standard
153 colors (ISO-6429). <EM>curses</EM> also assumes that <STRONG>COLOR_BLACK</STRONG> is the default
154 background color for all terminals.
156 <STRONG>COLOR_BLACK</STRONG>
157 <STRONG>COLOR_RED</STRONG>
158 <STRONG>COLOR_GREEN</STRONG>
159 <STRONG>COLOR_YELLOW</STRONG>
160 <STRONG>COLOR_BLUE</STRONG>
161 <STRONG>COLOR_MAGENTA</STRONG>
162 <STRONG>COLOR_CYAN</STRONG>
163 <STRONG>COLOR_WHITE</STRONG>
165 Some terminals support more than the eight (8) "ANSI" colors. There
166 are no standard names for those additional colors.
169 </PRE><H2><a name="h2-VARIABLES">VARIABLES</a></H2><PRE>
171 </PRE><H3><a name="h3-COLORS">COLORS</a></H3><PRE>
172 is initialized by <STRONG>start_color</STRONG> to the maximum number of colors the
173 terminal can support.
176 </PRE><H3><a name="h3-COLOR_PAIRS">COLOR_PAIRS</a></H3><PRE>
177 is initialized by <STRONG>start_color</STRONG> to the maximum number of color pairs the
178 terminal can support. Often, its value is the product <STRONG>COLORS</STRONG> x <STRONG>COLORS</STRONG>,
179 but this is not always true.
181 <STRONG>o</STRONG> A few terminals use the HLS color space (see <STRONG>start_color</STRONG> below),
182 ignoring this rule; and
184 <STRONG>o</STRONG> terminals supporting a large number of colors are limited to the
185 number of color pairs that a <EM>signed</EM> <EM>short</EM> value can represent.
188 </PRE><H2><a name="h2-FUNCTIONS">FUNCTIONS</a></H2><PRE>
190 </PRE><H3><a name="h3-start_color">start_color</a></H3><PRE>
191 The <STRONG>start_color</STRONG> routine requires no arguments. It must be called if
192 the programmer wants to use colors, and before any other color
193 manipulation routine is called. It is good practice to call this
194 routine right after <STRONG>initscr</STRONG>. <STRONG>start_color</STRONG> does this:
196 <STRONG>o</STRONG> It initializes two global variables, <STRONG>COLORS</STRONG> and <STRONG>COLOR_PAIRS</STRONG>
197 (respectively defining the maximum number of colors and color pairs
198 the terminal can support).
200 <STRONG>o</STRONG> It initializes the special color pair <STRONG>0</STRONG> to the default foreground
201 and background colors. No other color pairs are initialized.
203 <STRONG>o</STRONG> It restores the colors on the terminal to the values they had when
204 the terminal was just turned on.
206 <STRONG>o</STRONG> If the terminal supports the <STRONG>initc</STRONG> (<STRONG>initialize_color</STRONG>) capability,
207 <STRONG>start_color</STRONG> initializes its internal table representing the red,
208 green, and blue components of the color palette.
210 The components depend on whether the terminal uses CGA (aka "ANSI")
211 or HLS (i.e., the <STRONG>hls</STRONG> (<STRONG>hue_lightness_saturation</STRONG>) capability is
212 set). The table is initialized first for eight basic colors
213 (black, red, green, yellow, blue, magenta, cyan, and white), using
214 weights that depend upon the CGA/HLS choice. For "ANSI" colors the
215 weights are <STRONG>680</STRONG> or <STRONG>0</STRONG> depending on whether the corresponding red,
216 green, or blue component is used or not. That permits using <STRONG>1000</STRONG>
217 to represent bold/bright colors. After the initial eight colors
218 (if the terminal supports more than eight colors) the components
219 are initialized using the same pattern, but with weights of <STRONG>1000</STRONG>.
220 SVr4 uses a similar scheme, but uses <STRONG>1000</STRONG> for the components of the
221 initial eight colors.
223 <STRONG>start_color</STRONG> does not attempt to set the terminal's color palette to
224 match its built-in table. An application may use <STRONG>init_color</STRONG> to
225 alter the internal table along with the terminal's color.
227 These limits apply to color values and color pairs. Values outside
228 these limits are not valid, and may result in a runtime error:
230 <STRONG>o</STRONG> <STRONG>COLORS</STRONG> corresponds to the terminal database's <STRONG>max_colors</STRONG>
231 capability, (see <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>).
233 <STRONG>o</STRONG> color values are expected to be in the range <STRONG>0</STRONG> to <STRONG>COLORS-1</STRONG>,
234 inclusive (including <STRONG>0</STRONG> and <STRONG>COLORS-1</STRONG>).
236 <STRONG>o</STRONG> a special color value <STRONG>-1</STRONG> is used in certain extended functions to
237 denote the <EM>default</EM> <EM>color</EM> (see <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>).
239 <STRONG>o</STRONG> <STRONG>COLOR_PAIRS</STRONG> corresponds to the terminal database's <STRONG>max_pairs</STRONG>
240 capability, (see <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>).
242 <STRONG>o</STRONG> valid color pair values are in the range <STRONG>1</STRONG> to <STRONG>COLOR_PAIRS-1</STRONG>,
245 <STRONG>o</STRONG> color pair <STRONG>0</STRONG> is special; it denotes "no color".
247 Color pair <STRONG>0</STRONG> is assumed to be white on black, but is actually
248 whatever the terminal implements before color is initialized. It
249 cannot be modified by the application.
252 </PRE><H3><a name="h3-has_colors">has_colors</a></H3><PRE>
253 The <STRONG>has_colors</STRONG> routine requires no arguments. It returns <STRONG>TRUE</STRONG> if the
254 terminal can manipulate colors; otherwise, it returns <STRONG>FALSE</STRONG>. This
255 routine facilitates writing terminal-independent programs. For
256 example, a programmer can use it to decide whether to use color or some
257 other video attribute.
260 </PRE><H3><a name="h3-can_change_color">can_change_color</a></H3><PRE>
261 The <STRONG>can_change_color</STRONG> routine requires no arguments. It returns <STRONG>TRUE</STRONG> if
262 the terminal supports colors and can change their definitions; other,
263 it returns <STRONG>FALSE</STRONG>. This routine facilitates writing terminal-
264 independent programs.
267 </PRE><H3><a name="h3-init_pair">init_pair</a></H3><PRE>
268 The <STRONG>init_pair</STRONG> routine changes the definition of a color pair. It takes
269 three arguments: the number of the color pair to be changed, the
270 foreground color number, and the background color number. For portable
273 <STRONG>o</STRONG> The first argument must be a valid color pair value. If default
274 colors are used (see <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>) the upper limit is
275 adjusted to allow for extra pairs which use a default color in
276 foreground and/or background.
278 <STRONG>o</STRONG> The second and third arguments must be valid color values.
280 If the color pair was previously initialized, the screen is refreshed
281 and all occurrences of that color pair are changed to the new
284 As an extension, <EM>ncurses</EM> allows you to set color pair <STRONG>0</STRONG> via the
285 <STRONG><A HREF="default_colors.3x.html">assume_default_colors(3x)</A></STRONG> routine, or to specify the use of default
286 colors (color number <STRONG>-1</STRONG>) if you first invoke the <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>
290 </PRE><H3><a name="h3-init_extended_pair">init_extended_pair</a></H3><PRE>
291 Because <STRONG>init_pair</STRONG> uses signed <STRONG>short</STRONG>s for its parameters, that limits
292 color pairs and color-values to 32767 on modern hardware. The
293 extension <STRONG>init_extended_pair</STRONG> uses <STRONG>int</STRONG>s for the color pair and color-
294 value, allowing a larger number of colors to be supported.
297 </PRE><H3><a name="h3-init_color">init_color</a></H3><PRE>
298 The <STRONG>init_color</STRONG> routine changes the definition of a color. It takes
299 four arguments: the number of the color to be changed followed by three
300 RGB values (for the amounts of red, green, and blue components).
302 <STRONG>o</STRONG> The first argument must be a valid color value; default colors are
303 not allowed here. (See the section <STRONG>Colors</STRONG> for the default color
306 <STRONG>o</STRONG> Each of the last three arguments must be a value in the range <STRONG>0</STRONG>
307 through <STRONG>1000</STRONG>.
309 When <STRONG>init_color</STRONG> is used, all occurrences of that color on the screen
310 immediately change to the new definition.
313 </PRE><H3><a name="h3-init_extended_color">init_extended_color</a></H3><PRE>
314 Because <STRONG>init_color</STRONG> uses signed <STRONG>short</STRONG>s for its parameters, that limits
315 color-values and their red, green, and blue components to 32767 on
316 modern hardware. The extension <STRONG>init_extended_color</STRONG> uses <STRONG>int</STRONG>s for the
317 color value and for setting the red, green, and blue components,
318 allowing a larger number of colors to be supported.
321 </PRE><H3><a name="h3-color_content">color_content</a></H3><PRE>
322 The <STRONG>color_content</STRONG> routine gives programmers a way to find the intensity
323 of the red, green, and blue (RGB) components in a color. It requires
324 four arguments: the color number, and three addresses of <STRONG>short</STRONG>s for
325 storing the information about the amounts of red, green, and blue
326 components in the given color.
328 <STRONG>o</STRONG> The first argument must be a valid color value, i.e., <STRONG>0</STRONG> through
329 <STRONG>COLORS-1</STRONG>, inclusive.
331 <STRONG>o</STRONG> The values that are stored at the addresses pointed to by the last
332 three arguments are in the range <STRONG>0</STRONG> (no component) through <STRONG>1000</STRONG>
333 (maximum amount of component), inclusive.
336 </PRE><H3><a name="h3-extended_color_content">extended_color_content</a></H3><PRE>
337 Because <STRONG>color_content</STRONG> uses signed <STRONG>short</STRONG>s for its parameters, that
338 limits color-values and their red, green, and blue components to 32767
339 on modern hardware. The extension <STRONG>extended_color_content</STRONG> uses <STRONG>int</STRONG>s for
340 the color value and for returning the red, green, and blue components,
341 allowing a larger number of colors to be supported.
344 </PRE><H3><a name="h3-pair_content">pair_content</a></H3><PRE>
345 The <STRONG>pair_content</STRONG> routine allows programmers to find out what colors a
346 given color pair consists of. It requires three arguments: the color
347 pair number, and two addresses of <STRONG>short</STRONG>s for storing the foreground and
348 the background color numbers.
350 <STRONG>o</STRONG> The first argument must be a valid color value, i.e., in the range
351 <STRONG>1</STRONG> through <STRONG>COLOR_PAIRS-1</STRONG>, inclusive.
353 <STRONG>o</STRONG> The values that are stored at the addresses pointed to by the
354 second and third arguments are in the range <STRONG>0</STRONG> through <STRONG>COLORS</STRONG>,
358 </PRE><H3><a name="h3-extended_pair_content">extended_pair_content</a></H3><PRE>
359 Because <STRONG>pair_content</STRONG> uses signed <STRONG>short</STRONG>s for its parameters, that limits
360 color pair and color-values to 32767 on modern hardware. The extension
361 <STRONG>extended_pair_content</STRONG> uses <STRONG>int</STRONG>s for the color pair and for returning
362 the foreground and background colors, allowing a larger number of
363 colors to be supported.
366 </PRE><H3><a name="h3-reset_color_pairs">reset_color_pairs</a></H3><PRE>
367 The extension <STRONG>reset_color_pairs</STRONG> tells <EM>ncurses</EM> to discard all of the
368 color pair information which was set with <STRONG>init_pair</STRONG>. It also touches
369 the current- and standard-screens, allowing an application to switch
370 color palettes rapidly.
373 </PRE><H3><a name="h3-COLOR_PAIR">COLOR_PAIR</a></H3><PRE>
374 <STRONG>COLOR_PAIR(</STRONG><EM>n</EM><STRONG>)</STRONG> converts a color pair number to an attribute. Attributes
375 can hold color pairs in the range 0 to 255. If you need a color pair
376 larger than that, you must use functions such as <STRONG>attr_set</STRONG> (which pass
377 the color pair as a separate parameter) rather than the legacy
378 functions such as <STRONG>attrset</STRONG>.
381 </PRE><H3><a name="h3-PAIR_NUMBER">PAIR_NUMBER</a></H3><PRE>
382 <STRONG>PAIR_NUMBER(</STRONG><EM>attr</EM>) extracts the color information from its <EM>attr</EM>
383 parameter and returns it as a color pair number; it is the inverse
384 operation of <STRONG>COLOR_PAIR</STRONG>.
387 </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
388 The routines <STRONG>can_change_color</STRONG> and <STRONG>has_colors</STRONG> return <STRONG>TRUE</STRONG> or <STRONG>FALSE</STRONG>.
390 All other routines return the integer <STRONG>ERR</STRONG> upon failure and an <STRONG>OK</STRONG> (SVr4
391 specifies only "an integer value other than <STRONG>ERR</STRONG>") upon successful
394 X/Open defines no error conditions. SVr4 does document some error
395 conditions which apply in general:
397 <STRONG>o</STRONG> This implementation will return <STRONG>ERR</STRONG> on attempts to use color values
398 outside the range <STRONG>0</STRONG> to <STRONG>COLORS</STRONG>-1 (except for the default colors
399 extension), or use color pairs outside the range <STRONG>0</STRONG> to
400 <STRONG>COLOR_PAIRS-1</STRONG>.
402 Color values used in <STRONG>init_color</STRONG> must be in the range <STRONG>0</STRONG> to <STRONG>1000</STRONG>.
404 An error is returned from all functions if the terminal has not
407 An error is returned from secondary functions such as <STRONG>init_pair</STRONG> if
408 <STRONG>start_color</STRONG> was not called.
410 <STRONG>o</STRONG> SVr4 does much the same, except that it returns <STRONG>ERR</STRONG> from
411 <STRONG>pair_content</STRONG> if the pair was not initialized using <STRONG>init_pairs</STRONG> and
412 it returns <STRONG>ERR</STRONG> from <STRONG>color_content</STRONG> if the terminal does not support
415 This implementation does not return <STRONG>ERR</STRONG> for either case.
417 Specific functions make additional checks:
419 <STRONG>init_color</STRONG>
420 returns an error if the terminal does not support this feature,
421 e.g., if the <STRONG>initialize_color</STRONG> capability is absent from the
422 terminal description.
424 <STRONG>start_color</STRONG>
425 returns an error if the color table cannot be allocated.
428 </PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
429 In the <EM>ncurses</EM> implementation, there is a separate color activation
430 flag, color palette, color pairs table, and associated <STRONG>COLORS</STRONG> and
431 <STRONG>COLOR_PAIRS</STRONG> counts for each screen; the <STRONG>start_color</STRONG> function only
432 affects the current screen. The SVr4/XSI interface is not really
433 designed with this in mind, and historical implementations may use a
434 single shared color palette.
436 Setting an implicit background color via a color pair affects only
437 character cells that a character write operation explicitly touches.
438 To change the background color used when parts of a window are blanked
439 by erasing or scrolling operations, see <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>.
441 Several caveats apply on older x86 machines (e.g., i386, i486) with
442 VGA-compatible graphics:
444 <STRONG>o</STRONG> COLOR_YELLOW is actually brown. To get yellow, use COLOR_YELLOW
445 combined with the <STRONG>A_BOLD</STRONG> attribute.
447 <STRONG>o</STRONG> The A_BLINK attribute should in theory cause the background to go
448 bright. This often fails to work, and even some cards for which it
449 mostly works (such as the Paradise and compatibles) do the wrong
450 thing when you try to set a bright "yellow" background (you get a
451 blinking yellow foreground instead).
453 <STRONG>o</STRONG> Color RGB values are not settable.
456 </PRE><H2><a name="h2-EXTENSIONS">EXTENSIONS</a></H2><PRE>
457 The functions marked as extensions were designed for <STRONG><A HREF="ncurses.3x.html">ncurses(3x)</A></STRONG>, and
458 are not found in SVr4 <EM>curses</EM>, 4.4BSD <EM>curses</EM>, or any other previous
459 curses implementation.
462 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
463 Applications employing <EM>ncurses</EM> extensions should condition their use on
464 the visibility of the <STRONG>NCURSES_VERSION</STRONG> preprocessor macro.
466 This implementation satisfies X/Open Curses's minimum maximums for
467 <STRONG>COLORS</STRONG> and <STRONG>COLOR_PAIRS</STRONG>.
469 The <STRONG>init_pair</STRONG> routine accepts negative values of foreground and
470 background color to support the <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG> extension, but
471 only if that routine has been first invoked.
473 The assumption that <STRONG>COLOR_BLACK</STRONG> is the default background color for all
474 terminals can be modified using the <STRONG><A HREF="default_colors.3x.html">assume_default_colors(3x)</A></STRONG>
477 This implementation checks the pointers, e.g., for the values returned
478 by <STRONG>color_content</STRONG> and <STRONG>pair_content</STRONG>, and will treat those as optional
479 parameters when null.
481 X/Open Curses does not specify a limit for the number of colors and
482 color pairs which a terminal can support. However, in its use of <STRONG>short</STRONG>
483 for the parameters, it carries over SVr4's implementation detail for
484 the compiled terminfo database, which uses signed 16-bit numbers. This
485 implementation provides extended versions of those functions which use
486 <STRONG>short</STRONG> parameters, allowing applications to use larger color- and pair-
489 The <STRONG>reset_color_pairs</STRONG> function is an extension of <EM>ncurses</EM>.
492 </PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
493 SVr3.2 introduced color support to curses in 1987.
495 SVr4 made internal changes, e.g., moving the storage for the color
496 state from <STRONG>SP</STRONG> (the <EM>SCREEN</EM> structure) to <STRONG>cur_term</STRONG> (the <EM>TERMINAL</EM>
497 structure), but provided the same set of library functions.
499 SVr4 curses limits the number of color pairs to 64, reserving color
500 pair zero (0) as the terminal's initial uncolored state. This limit
501 arises because the color pair information is a bitfield in the <STRONG>chtype</STRONG>
502 data type (denoted by <STRONG>A_COLOR</STRONG>).
504 Other implementations of curses had different limits:
506 <STRONG>o</STRONG> PCCurses (1987-1990) provided for only eight (8) colors.
508 <STRONG>o</STRONG> PDCurses (1992-present) inherited the 8-color limitation from
509 PCCurses, but changed this to 256 in version 2.5 (2001), along with
510 changing <STRONG>chtype</STRONG> from 16-bits to 32-bits.
512 <STRONG>o</STRONG> X/Open Curses (1992-present) added a new structure <STRONG>cchar_t</STRONG> to store
513 the character, attributes and color pair values, allowing increased
514 range of color pairs. Both color pairs and color-values used a
515 signed <STRONG>short</STRONG>, limiting values to 15 bits.
517 <STRONG>o</STRONG> <EM>ncurses</EM> (1992-present) uses eight bits for <STRONG>A_COLOR</STRONG> in <STRONG>chtype</STRONG>
520 Version 5.3 provided a wide-character interface (2002), but left
521 color pairs as part of the attributes-field.
523 Since version 6 (2015), ncurses uses a separate <STRONG>int</STRONG> for color pairs
524 in the <STRONG>cchar_t</STRONG> values. When those color pair values fit in 8 bits,
525 ncurses allows color pairs to be manipulated via the functions
526 using <STRONG>chtype</STRONG> values.
528 <STRONG>o</STRONG> NetBSD curses used 6 bits from 2000 (when colors were first
529 supported) until 2004. At that point, NetBSD changed to use 10
530 bits. As of 2021, that size is unchanged. Like <EM>ncurses</EM> before
531 version 6, the NetBSD color pair information is stored in the
532 attributes field of <STRONG>cchar_t</STRONG>, limiting the number of color pairs by
533 the size of the bitfield.
536 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
537 <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>, <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>, <STRONG><A HREF="curs_variables.3x.html">curs_variables(3x)</A></STRONG>,
538 <STRONG><A HREF="default_colors.3x.html">default_colors(3x)</A></STRONG>
542 ncurses 6.5 2024-04-20 <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>
546 <li><a href="#h2-NAME">NAME</a></li>
547 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
548 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
550 <li><a href="#h3-Overview">Overview</a></li>
551 <li><a href="#h3-Rendering">Rendering</a></li>
554 <li><a href="#h2-CONSTANTS">CONSTANTS</a></li>
555 <li><a href="#h2-VARIABLES">VARIABLES</a>
557 <li><a href="#h3-COLORS">COLORS</a></li>
558 <li><a href="#h3-COLOR_PAIRS">COLOR_PAIRS</a></li>
561 <li><a href="#h2-FUNCTIONS">FUNCTIONS</a>
563 <li><a href="#h3-start_color">start_color</a></li>
564 <li><a href="#h3-has_colors">has_colors</a></li>
565 <li><a href="#h3-can_change_color">can_change_color</a></li>
566 <li><a href="#h3-init_pair">init_pair</a></li>
567 <li><a href="#h3-init_extended_pair">init_extended_pair</a></li>
568 <li><a href="#h3-init_color">init_color</a></li>
569 <li><a href="#h3-init_extended_color">init_extended_color</a></li>
570 <li><a href="#h3-color_content">color_content</a></li>
571 <li><a href="#h3-extended_color_content">extended_color_content</a></li>
572 <li><a href="#h3-pair_content">pair_content</a></li>
573 <li><a href="#h3-extended_pair_content">extended_pair_content</a></li>
574 <li><a href="#h3-reset_color_pairs">reset_color_pairs</a></li>
575 <li><a href="#h3-COLOR_PAIR">COLOR_PAIR</a></li>
576 <li><a href="#h3-PAIR_NUMBER">PAIR_NUMBER</a></li>
579 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
580 <li><a href="#h2-NOTES">NOTES</a></li>
581 <li><a href="#h2-EXTENSIONS">EXTENSIONS</a></li>
582 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
583 <li><a href="#h2-HISTORY">HISTORY</a></li>
584 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>